Traffic control system



Mmh 24,1942. C; Mac/LUSTER ,2,277,495

TRAFFIC CONTROL SYSTEM Filed Deo. 4, 1941 His tbov'eg Patented Mar. 24, 1942 TRAFFIC CONTROL SYSTEM Copeland MacAllister, Winchesteig Mass., assigner to General Electric Company, a corporation of New York Application December 4, 1941, Serial No. 421,669

3 Claims.

My invention'relates to trac control systems and more particularly to a traic control system comprising a group of intersection controllers controlled by a common master controller and interconnected therewith by a relatively long con- `rol cable.

One object-oi my invention is to provide an interconnecting control cable in which voltages induced in the idle conductors of the cable by control impulses sent out over the periodically selected conductors of the cable are made ineiective to operate apparatuscontrolled through the idle conductors.

For a better understanding of my invention, together with other and further objects thereof, reference is had to the following description taken in connection with the accompanying drawing, and its scope will be pointed out in the appended claims.

The accompanying drawing illustrates diagrammatically a traflic control system embodying my invention.

Referring to this drawing in detail, a master controller l0 is connected to control secondary controllers of Which only one is illustrated in this drawing, the connecting conductors to one other secondary controller being indicated. The secondary controller operates groups of traic signals I2 and I2 which are connected to the controller is preferably of the type fully described controller by a suitable cable I3. The secondary in application S. N. 416,969, led October 29, 1941, by R. A. Reid. This controller includes a suitable contact mechanism for sequentially energizing the signals |2, I2'. be of any well-known construction and is indicated merely by a rectangle li. Its operation is controlled by a timing dial 14 mounted on av shaft l5 and driven by 'a motor I6 through its shaft l1 and a pair of cooperating gears I3 and i9. The timing dial is provided with two concentric rows of radial slots 23 and 2| in each of which a group of keys or switch actuators is spaced in accordance with a desired program.` Keys 22 to 23 are provided in theouter row of slots and keys 21 to 3| are provided in the inner row of slots for respectively actuating switch contacts 32 and 33. The switch Contact 32 is mounted upon a suitable resilient contact arm 34 to the free end of which is attached an actuating block 35. the actuating block projects into the path of the actuators in the outer row of slots 2li, and as each actuator passes the actuating block, the contact is raised to engage a cooperating Contact 36 thereby establishing a circuit from a common |This mechanism may I2 The end of 5" conductor 31, which is connected to a source of power and from which current is supplied, through conductors 38 and 39 to the contact 36. The circuit continues from contact 33 to contact 32, contact arm 34, conductor 40'to a switch terminal 4|.

The inner row of actuators, 21 to,3|, actuate the contact 33 which is mounted upon a resilient contact arm 42 mounted parallel to the contact arm 34 and is provided with an actuating block 43. As the actuators 21 to 3|r move under the end of the actuating block 43 the actuating block with the contact 33 is raised to engage a contact 44 thereby to close a circuit from the conductor 31 through conductors 38, 39 and 45 to the contacts 44, 33, Contact arm 42, conductor 43 to switch 41 and from switch 41 to the contact mechanism through a conductor 48.

The switch 41 is a two-position switch which may be moved from the position in which it is illustrated to a position in which it engages the terminal 4|. In case the switch is so moved the circuit between conductors 46 and 43 is broken by the switch and a circuit is established between the conductor 40 and the conductor 43. When the switch 41 is in the position illustrated, the inner row of actuators is effective to operate the contact mechanism il', the operating circuit being established from the source conductor 31 through the second pair of contacts 44, 33 to the Controller. In the second position of this switch 41 the operating circuit to the switch mechanism may be completed by the rst ypair of contacts 32, 35 actuated by the outer row of actuators on the timing dial. Since each group of actuators is arranged in accordance with a predetermined program, the switch 41 is the secondary program selectorswitch.

The program switch 41 is operated by magnets 53 and 5| which actuate through their respective armatures a link member 52 connected to the armatures and to the switch 41. When coil 5l! is energized, the link member is drawn upwardly to place the switch in the position shown, and when coil 5 I is energized, the link and switch are drawn downwardly to establish a circuit between contact 4| and the conductor` 43. The coil 50 is connected by a conductor 53 to a common conductor 54 of the interconnecting cable for the system. This common conductor is one of several conductors which connect this controller to the master controller lil. Other controllers are connected to these conductors as indicated, for example, by the conductor 53. This conductor 54 terminates in the master controller at contacts 55 and 56 of a relay 51. This relay 51 is provided, in accordance with my invention, to connect the conductor to a source of power when a control impulse is to be sent from the master controller to the secondary controllers and to connect this conductor to ground when the control impulse is ended.

'I'he relay 51 is provided with an operating coil 58 which is energized by the operation of a master selector switch 59. When this switch is in the position in which it is shown in the drawing, it completes a circuit to the coil 58, through a conductor 68 iromthe source conductor 31. The coil is grounded at its opposite end. When the coil is so energized the relay is operated to close a circuit to the conductor 54, through terminals 55, 6|, conductor 60 and source conductor 31. The secondary controller coils 50, being connected to the conductor 54 through conductors 53, 53', are each energized to move the corresponding secondary selector switch 41 to its upper position. When the master switch 59 is opened to deenergize the coil 58, the relay is operated to close a circuit from the terminal 56 to a terminal 62 and through a conductor 63 to ground.

The coil of the secondary switch 41 is connected by a conductor 64 to a second common conductor 65 which extends to the master controller terminating in contacts 66, 81 of a relay 68, which relay, being in a deenergized position, establishes a circuit to ground through its contacts 61, 69 and grounded conductor 18. The coil 1| of this relay is grounded at one 'end and at the other end is connected by a conductor 12 to a contact 13 of the switch 59. This manually operated master selector switch 59 may be moved to engage this contact 13 thereby to energize the relay coil 1| from the source conductor 31 through the conductor 60. When so energized, the relay 68 is operated to establish a circuit from the contact 66 and the conductor 85 to a contact 14 and through a conductor- 15 to the conductor 68 thereby completing the circuit from source conductor 31 to the coil 5| which is grounded at its opposite end.

The motor I6 is normally driven by a eld 16 energized from the source conductor 31 through the conductor 38, a conductor 11 and a manually operated switch 18. The motor is also provided with a braking eld 80 which when energized tends to drive the motor in an opposite direction and thereby holds the motor stationary when ield 16 is energized. This ield is energized only when the dial I4 is not in its proper operating relation to the master controller and is energized by the movement of a special key 8| placed in the inner row of slots 2| to actuate an actuating block 82. This key is provided with a slot 8| so that it will not actuate the actuating block 43. The actuating block 82 is attached to a contact arm 83 which is mounted parallel to contact arm 42 and carries a contact 84. When the contact 84 is raised it engages a cooperating contact 85 to establish a circuit to the field 88 which may be traced from the grounded end of the field 80 through the eld to a conductor 88, the contacts 84, 85, contact arm 83, conductor 81 to a common conductor 88 terminating at the master controller at contacts 89, 90 of a relay 9|. The relay is in its energized position and connects contact 89 to a contact 92 which is connected by a conductor 93 to the conductor 60 and thereby to the source conductor 31. The relay 9| is provided with an operating coil 94 which is grounded at one end and receives energy through a conductor-95, a pair of closed contacts 96, 91, conductor 60 and soure conductor 31. The contactsA 96, 91 are normally closed. Contact 96 is, however, mounted upon a supporting arm 98 which is raised by a cam 99 provided with a projection |00. This operation is such that the contacts are separated momentarily once during each cycle of trailic signal operations. When the contacts are separated the coil 94 is deenergized thereby dropping the relay to its second position at which the conductor 88 is connected to ground through contact 90, relay 9|, contact |02 and grounded conductor |03. Under proper operating relationship, that is when the controllers are in synchronism, the actuating key 8| closes the circuit for eld 80 by the actuation of the contact 84 at the same instant that the cam projection |00 effects a separation of the contacts 95, 91, thereby opening the circuit to the eld at the instant at which the secondary controller attempts to close it. The secondary controller thereby is permitted to continue operation whereby it again opens the circuit at the contacts 84 and 85 and the reclosure of the master contacts 96, 91 becomes ineffective to Stop the dm I4. In case the dial I4 and the cam |08 are o ut of proper operating relationship i', f or out of synchronism., the circuit to iield 80 is :i

completed and the dial |4 is held stationary with the contacts 84, closed until the cam- |60 is rotated to the position at which it separates the contacts 96, 91.

The relays 51, 68 and 9| are provided in the common conductors 54, 85 and 88 in accordance with my invention. The operating coil of each of these relays is energized when it is desired to send out a control impulse over its respective common conductor, the relay being thereby operated to connect its common conductor to a source of power. The coil is deenergized when the control is effected. The relay then breaks the connection between its conductor and the source of power and establishes a circuit to ground for its conductor. In the drawing, the conductor 65 is grounded while the conductors 54 and 88 are energized through the relays 51 and 9|. When selector switch 59 is moved to its second position toA engage the contact 13, the coil 58 of the relay 51 becomes deenergized and the relay drops to establish a circuit to ground for the conductor 54. The relay coil 1| is then energized through the switch 59, breaks its ground circuit to the conductor 65 and establishes a current path through its contacts 86, 14 to the conductors 15, 68 and 31.

It has been found that in long cables to which other controllers may be connected by groups of conductors such as 38', 53', 64 and 81', the capacitative inductance between conductors is of such magnitude that when one of the conductors of the cable is energized or deenergized, an induced voltage arises in the other conductors, which are idle at that instant, which voltage is at times great enough to operate the selector switches or other apparatus connected to these conductors in the secondary controllers. In accordance with my invention the relays that are provided at the master controller for each conductor of the interconnecting control cable connect each conductor to ground, except the one which is energized to effect a control operation. All induced currents in the idle conductors are thereby immediately discharged to ground` and their potential does not buildup sufliciently said conductors respectively at the end of each energization period.

2. In a traic signal system, the combination of a master controller, a group of secondary controllers, conductors interconnecting said controllers, master switches in said master con-l troller, and relays between said master switches and said conductors arranged normally to estab-l lish a ground connection for each of said conductors, and successively to break said ground connections responsive to the operation of said respective master switches and to connect said conductors to a source of current.

3. In a traiiic signal system, the combination of a master controller, a group of secondary controllers, conductors interconnecting said controllers, relays in said master controller arranged individually to connect said conductors to ground and when energized to break said ground connection and to establish a connection between said conductors and a source of energy, and means in said master controller for periodically energizing the operating coils of said relays thereby to break said V)ground connection and to connect said conductors to a source of energy.

COPELAND MACALLISTER.

sam-e Amay conform to the record of the case in the Patent CERTIFICATE oF co RREcTioN. Patent No. 2,277,LL95. March zu, 19in.

COPELAND MaCALLISTER.

It is hereby certified that error appears inl the printed specification of the above numbered patent requiring correction as follows: Page l first "controller is preferably of the type fully and that the that the column, line 50 strike out described" and insert the same after "secondary" in line 5l;

Letters Patent should be read with this correction therein Office said signed and sealed this 19th day of May, A. D. 19m.

Henry Van Arsdale,

(Seal) 'Acting Commissioner of Patents. 

